Currently, both manual and automated blood culture systems are available, with the market being dominated increasingly by instrument-based automated systems and methods. This chapter will emphasize those manual and automated systems and media cleared for diagnostic use in the United States at the start of the 21st century as well as comment on possible developments in the rapidly evolving area of clinical microbiology. The fundamental concept of blood culturing has been based on inoculating a defined volume of blood, preferably obtained by a sterile venipuncture, into a broth culture medium that will support the growth of most pathogenic bacteria and fungi. In a study that compared the aerobic FAN bottle to the aerobic 80A bottle, more contaminants were detected in the FAN bottle, and the ESP system had more instrument false-positive readings. Cockerill and colleagues compared the ESP 80A bottle to the Isolator and found that the former recovered more coagulase-negative staphylococci causing bacteremia, whereas the latter recovered more S. aureus, Candida spp., and all microorganisms combined. In this study, the ESP 80A bottle also was compared to the manual Septi-Chek bottle and found to be equivalent in the recovery of microorganisms. Although current blood culture systems have reduced the time to detecting positive cultures, clinicians and patients still would benefit from accurate assay methods that provide results in minutes to hours as opposed to days. Thus, there continues to be a need for further evolution and development of new commercial blood culture systems.